A method of processing the surface of a workpiece using an adaptive gas cluster ion beam is disclosed. The invention provides a method of reducing the surface roughness and/or improving the surface smoothing of a workpiece by etching at various etch rates. The workpiece is initially processed with a gas cluster ion beam having an initial etch rate and then the beam is adjusted so that the workpiece is processed with one or more lower etch rates. The advantages are minimum required processing time, minimum remaining roughness of the final surface, and minimum material removal in order to attain a desired level of smoothness.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of processing a surface of a workpiece using an adaptive gas cluster ion beam wherein the processing of the surface comprises cleaning, smoothing, or etching the surface comprising: providing a pressurized gaseous source material; flowing the pressurized gaseous source material through a nozzle into a reduced-pressure chamber to form a jet of gas clusters: ionizing the jet of gas clusters to form a gas cluster ion beam; exposing the surface of the workpiece to the gas cluster ion beam wherein the gas cluster ion beam has an initial processing rate of cleaning, smoothing or etching; monitoring a workpiece surface condition; computing process parameters; adapting the gas cluster ion beam during processing, based on said computing, so that the gas cluster ion beam then has at least one other processing rate, the at least one other processing rate being lower than the initial processing rate.
2. The method of claim 1 , wherein the adapting step comprises adjusting ion acceleration potential of the gas cluster ion beam.
3. The method of claim 1 , wherein the adapting step comprises adjusting ion beam current or beam current density of the gas cluster ion beam.
4. The method of claim 1 , wherein the adapting step comprises adjusting fraction of multiply-ionized clusters of the gas cluster ion beam.
5. The method of claim 1 , wherein the adapting step comprises adjusting the mean charge state of clusters of the gas cluster ion beam.
6. The method of claim 1 , wherein the adjusting step comprises adjusting source gas pressure or temperature thereby altering the cluster-size distribution of the gas cluster ion beam.
7. The method of claim 1 , wherein the adapting step comprises adjusting source gas composition of the gas cluster ion beam.
8. The method of claim 7 , wherein the source gas composition is selected from the group consisting of argon, oxygen, nitrogen, sulfur hexafluoride, a halogen, a halogen containing compound, nitric oxide and carbon dioxide, any mixture thereof, and mixture with hydrogen or helium.
9. The method of claim 1 , wherein the gas cluster ion beam is formed using an argon gas and the gas cluster ion beam has a broad cluster size distribution having most-probable sizes between 500 and 5000 atoms.
10. The method of claim 9 , wherein the gas cluster ion beam is formed with an initial acceleration voltage greater than or equal to about 15,000 volts.
11. The method of claim 10 , wherein the adapting step comprises reducing the initial acceleration voltage to at least one other acceleration voltage.
12. The method of claim 11 , wherein the at least one other acceleration voltage is greater than or equal to about 5,000 volts.
13. The method of claim 11 , wherein the initial acceleration voltage ranges from about 30,000 volts to about 50,000 volts and the at least one other acceleration voltage ranges from about 5,000 volts to about 7,000 volts.
14. The method of claim 1 , wherein the gas cluster ion beam is formed using an argon gas, the gas cluster ion beam is accelerated by a fixed voltage ranging from about 7,000 volts to about 30,000 volts and the gas cluster ion beam has a broad cluster size distribution with most-probable sizes between 100 and 1,000 atoms.
15. The method of claim 14 , wherein the adapting step comprises increasing the size distribution to a most-probable size of 5,000 to 50,000 atoms.
16. The method of claim 1 , wherein the gas cluster ion beam is formed using an argon gas, the gas cluster ion beam has a cluster-size distribution with most-probable sizes between 500 to 5,000 atoms, and the gas cluster ion beam has an initial beam current density greater than or equal to 10 A/cm 2 .
17. The method of claim 16 , wherein the adapting step comprises reducing the initial beam current density to at least one other beam current density wherein the at least one other beam current density is less than or equal to 1 A/cm 2 .
18. The method of claim 1 , wherein the gas cluster ion beam is initially composed of clusters relatively cold compared with the freezing point of a source gas.
19. The method of claim 18 , wherein the adapting step comprises warming the clusters to a higher temperature wherein the higher temperature is less than a condensation liquefaction temperature of the source gas.
20. The method of claim 1 , wherein the gas cluster ion beam is formed using an argon gas mixed with an additional gas, wherein the additional gas is selected from the group consisting of oxygen, a halogen, and a halogen-containing compound thereby providing a more isomorphic etch rate on the surface of the workpiece wherein the workpiece is composed of two or more compositions.
21. The method of claim 20 , wherein the adapting step comprises reducing the percentage of the additional gas in the gas mixture as the processing proceeds thereby rendering the surface of the workpiece nearly planar and smooth.
22. The method of claim 1 , wherein the adapting step includes adjusting one or more parameters, wherein the parameters are selected from the group consisting of source gas composition, source gas temperature, gas cluster size, gas cluster charge state, beam acceleration potential, ion beam current, and ion beam current density.
23. The method of claim 1 further comprising monitoring the surface of the workpiece during processing in order to provide information about the surface, wherein the monitoring step is performed after the exposing step and before the adapting step.
24. The method of claim 23 , wherein the information is surface roughness, surface smoothness, etch depth, or surface contamination.
25. The method of claim 23 , wherein the adapting step is automatically performed based on the information provided during the monitoring step.
26. The method of claim 23 , wherein the monitoring step and the adapting step are repeated at least once.
27. The method of claim 23 , wherein the monitoring step is accomplished by an optical roughness monitor.
28. A method of processing a surface of a workpiece using an adaptive gas cluster ion beam comprising: forming a gas cluster ion beam; exposing the surface of the workpiece to the gas cluster ion beam wherein the gas cluster ion beam has an initial processing rate; adapting the gas cluster ion beam during processing wherein the gas cluster ion beam has at least one other processing rate, the at least one other processing rate being lower than the initial processing rate; wherein the gas cluster ion beam is formed with an initial acceleration voltage wherein the initial acceleration voltage ranges from about half a predetermined etching threshold value to about the predetermined etching threshold value and the exposing step is for a sufficient length of time to remove a substantial amount of contamination from the surface.
29. The method of claim 28 , wherein the adapting step further comprises adjusting the initial acceleration voltage to at least one other acceleration voltage wherein the at least one other acceleration voltage is greater than the predetermined etching threshold value and greater than 15,000 volts, and then the at least one other acceleration voltage is reduced to a value greater than or equal to about 5,000 volts.
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October 31, 2001
October 19, 2004
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